A chirp-generator comprising a phase-detector for providing a phase-difference-signal representative of a phase difference between a clock-input-signal and a feedback-signal. A VCO-circuit is configured to provide a chirp-generator-output-signal based on the phase-difference-signal. The VCO-circuit comprises a switched-varactor-bank, which includes a plurality of varactors, and a varactor-switch associated with each of the plurality of varactors. The varactor-switch is configured to selectively control whether or not the associated varactor contributes to the capacitance of the VCO-circuit, based on the state of a varactor-control-signal. The chirp-generator also includes a feedback-component configured to: receive the chirp-generator-output-signal; and apply a variable-multiplication-factor to the chirp-generator-output-signal in order to provide the feedback signal for the phase-detector. A controller provides a sequence of different variable-multiplication-factors to the feedback-component; and provides varactor-control-signals to the plurality of varactors such that the varactors are sequentially controlled such that they contribute to the capacitance of the VCO-circuit.